In recent years, fuel-driven internal combustion engines, in which the fuel is injected directly into the cylinders, have come to the fore; in these engines, the fuel is supplied under pressure to a fuel manifold connected to a series of injectors (one for each cylinder of the engine), which are actuated cyclically to inject part of the fuel under pressure in the fuel manifold into a respective cylinder.
In known engines with indirect fuel injection, the fuel manifolds are currently made from plastic material (typically moulded technopolymers) and are secured to the intake manifold, which is also generally made from plastic material, by means of a series of screws. Plastic material is easy to process and extremely economic, but does not have good mechanical properties and is not therefore able to bear the relatively high pressures of the fuel used in direct fuel injection with the necessary safety margins.
In order to ensure the necessary mechanical strength, it has been proposed to use fuel manifolds made from steel in known direct fuel injection engines; these fuel manifolds are nevertheless costly because of the number of machining and welding operations to which they have to be subject. It has also been proposed to use fuel manifolds made from cast aluminum by means of gravity die casting; these fuel manifolds are also costly as gravity die casting is a relatively slow production method, requires a large number of machining operations once the component has been removed from the casting mould and imposes minimum component thicknesses of no less than 4–5 mm.